An initial step in the electrophotographic printing process includes the deposition of a charge onto the surface of the photoconductor. Additionally, the photoconductor is discharged by selectively exposing the surface of the photoconductor to a scanning laser beam to form a latent electrostatic image. After formation of the latent electrostatic image, toner is developed onto the surface of the photoconductor drum during development.
One type of commonly used technique for the development of toner onto the latent electrostatic on the surface of the photoconductor is jump gap development. In the jump gap development process, an electrical signal is applied to a developer roller located close to the surface of the photoconductor. The gap between the surface of the photoconductor and the sleeve of the developer roller is usually in the range of several hundred microns. The electrical signal typically includes a DC component of the developer bias having a superimposed sinusoidal or square wave AC signal.
The charge on the surface of the photoconductor and the electrical signal applied to the developer roller create an electric field which moves electrically charged toner particles across the gap and onto the surface of the photoconductor. The combination of the AC and DC components of the electrical signal applied to the developer roller provides the electric field that strips toner off the sleeve of the developer roller and helps remove toner from the areas on the surface of the photoconductor which are not part of the latent electrostatic image.
The jump gap development process works well for the development of the interior portions of discharged areas on the surface of the photoconductor. However, in some cases, the jump gap development process does not fully develop the edges of the discharged areas. This can contribute to a degradation in the perceived quality of the printed image because the lack of development of edge detail. Furthermore, color printing is particularly susceptible to print quality problems resulting from jump gap development. Because high quality color printing requires, not only the capability to develop the fine features of images, but also the capability to precisely control the developed amounts of the various colored toners to accurately reproduce the desired colors, the shortcomings of the jump gap development process can be especially noticeable in color printing. Improving the performance of the jump gap development process provides a way in which the demands for improved print quality in electrophotographic printing can be met.